Effect of additional constraints of push-out test on the mechanical properties of perfobond shear connectors

Abstract

Perfobond shear connector is widely used in steel–concrete composite structures due to its high ultimate shear capacity, large shear stiffness, and excellent fatigue resistance. The mechanical properties of perfobond connectors are mainly studied by the push-out test. However, the confinement effect caused by the contact friction at the bottom of push-out specimens does not exist in the actual structures. There is also a significant difference in the confinement effect caused by the restrained rebar in the actual structures and push-out specimens. This confinement effect on perfobond connectors may overestimate the shear capacity based on the conventional push-out test. To accurately evaluate the shear capacity of perfobond connectors, four groups of push-out tests are carried out. The effect of the restrained rebar and contact friction on the mechanical properties of perfobond connectors is studied. The test results indicate that the shear capacity of the connectors increase by 19 % under the effect of restrained rebar. However, the improvement of shear stiffness and ductility is slight. Under the effect of contact friction, the shear capacity, the representative slip S0.9U, and representative shear stiffness K0.5U are increased by 24%, 136%, and 31%, respectively. This indicates that the friction force can significantly improve the shear capacity, shear stiffness, and ductility of connectors. The influencing mechanism of the restrained rebar and contact friction on the mechanical properties of connectors is clarified, and a simplified mechanical model of the perfobond connectors is proposed. Finally, an empirical formulae is proposed for the shear capacity of perfobond connectors considering the effect of additional confinement, based on the simplified mechanical model. The shear capacity of the perfobond connectors was predicted well by the proposed formulae.